Diagnostic arrangement for automotive engine EGR system

摘要

When the engine throttle valve is closed or very nearly closed, the induction vacuum assumes a level whereat the flow of exhaust gas through the EGR conduit can be induced to assume a sonic level and maximize. Under these conditions, by opening the EGR control valve and checking the change in induction pressure, the amount of recirculation can be monitored in a manner which enables partial EGR conduit blockage and/or similar types of malfunctions to be detected.